i change light and contrast, and if the pic is to red or yellow i make it more neutral.
and since i go to a media school i've been learning to use photoshop and i love using it, i'm pretty addicted.
don't find it hot though when people overdoes it and look plastic! ;__;

But I never use it for major alterations like making yourself really skinny and look nothing like you anymore. That just shows how much you're insecure with what you look like. [If you wanna get skinny, exercise]

But as mentioned by others before, photoshop is a way to make a picture jump out and to get yourself in a creative and artsy move.